1. Field of the Invention
The present invention relates to an image recording method and an image recording apparatus, and more especially to an image recording method and an image recoding apparatus for, e.g., an apparatus for performing main-scanning of a recording medium to be sub-scanned and transferred, and then recording an image, in which the image is dispersion-recorded in a direction of sub-scanning.
2. Description of the Related Art
Conventionally, an image recording apparatus using a thermal head to record an image on a recording medium, has widely been used. Image recording apparatus like this, a thermal recording material, which is the recording medium, is pressed onto a line-type thermal head on which a plurality of heating elements are arranged in one-dimensional direction. While the heating elements are being controlled respectively in response to image data, the thermal recording material is transferred in a direction perpendicular to the one-dimensional direction, resulting in recording a desired two-dimensional gradation image.
In this case, the gradation image is formed as shown in FIG. 4A. Namely, the image of gradation D=1 is formed by activating the heating elements for t [seconds]. Further, the image of gradation D=2 is formed by activating the heating elements for 2t [seconds]. Similarly, the images of gradation D=3 to D=5 are formed by heating the heating elements for 3t to 5t [seconds], respectively.
Thus, pixels having different light-emission areas in accordance with gradation are formed on the thermal recording medium within a single pixel width in the transfer direction, as shown in FIG. 4B. Thereby, a gradation image is recorded. In the above example, a case of modulation of the pulse width has been described. However, even in a case of modulation of a number of pulses, a gradation image is recorded in substantially the same manner as in a case of modulation of the pulse width as above.
Incidentally, when a gradation image is recorded like this, each pixel is always recorded from a constant point (point xe2x80x9caxe2x80x9d in FIG. 4A). Since the point xe2x80x9cbxe2x80x9d side in a single pixel width in the transfer direction becomes non-recorded portion, the recorded image becomes concentrated on the point xe2x80x9caxe2x80x9d side as above. Therefore, when a formed two-dimensional image is viewed over its entirety, there occurs a drawback that the image becomes conspicuously coarse.
In order to overcome this drawback, it is effective to dispersion-record the image data. Various types of technologies therefor have been proposed. For example, the technology of xe2x80x9cImage Recording Method and Apparatusxe2x80x9d disclosed in JP 07-96625 A corresponded to an application made by the assignee for the present invention also can be given as one example of such a technology.
According to this technology, when the image is one-dimensionally recorded on the recording medium using an image recording unit, and either the recording medium or the image recording unit is moved in a direction perpendicular to the one-dimensional direction to record the image, and simultaneously, the multi-gradation image data of each of pixels constituting the image are divided into a plurality of substantially equal portions of image data. Based on this plurality of divided image data, the image is dispersed in a direction in which the recording medium or the image recording unit, is moved and thus recorded.
According to this technology, the image data of each of the pixels constituting the image is divided into a plurality of substantially equal portions of image data. Based on the divided image data, the image is dispersed in a direction in which the recording medium or the image recording unit is moved thereby recording the image. This produces the result that the roughness occurred in recording the two-dimensional gradation image disappears, and it becomes possible to perform a record with high image quality.
Further, in a technology of xe2x80x9cImage Recording Methodxe2x80x9d disclosed in JP 10-44509 A corresponded to an application which was also filed by the assignee for the present application, an image is recorded using an image recording unit in a one-dimensional manner onto a recording medium, and also, either the recording medium or the image recording unit is moved in a direction perpendicular to the one-dimensional direction to record the image, and the multi-gradation image data of the image elements constituting the image are divided into a plurality of number of substantially equal portions of image data. This image data is allotted to a part of the recording points that are divided into a number of the image data or more. Then, the image is dispersed in the moving direction in which the recording unit or the image recording unit is moved and thus recorded.
According to this technology, it becomes possible to prevent deterioration such fuzziness of the image quality in the low density areas, in which there has been a possibility of such deterioration occurring in the technology discussed above, and this makes it possible to apply the image dispersion-recording method more effectively.
However, even when this method is used, there occurs a recording sound caused by a solid image formed using the same thermal pulse (heating pulse). This is owing that between the heating body and the recording layer of heat sensitive recording material, burning-in caused by heating and fading at the time of transferring are repeated.
The present invention was developed in view of the above-mentioned problem. This invention has an object to provide an image recording method and apparatus capable of easily preventing a recording sound in the above-mentioned dispersion-recording technology from generating.
To obtain the object, an image recording method relating to the present invention is characterized by recording a pixel forming the image using a plurality of pulses having the step of shifting a thermal pattern between neighboring pixels to perform said image recording.
Further, it is preferable that the image recording method has the step of making a number of heating elements being activated, substantially uniform at each recording time.
The invention can be embodied as an image recording apparatus as below.
Namely, the image recording apparatus relating to the present invention is characterized by having an image recording unit which records an image in a direction, a transfer unit which transfers the image recording unit with relative to a recording medium, which are moved in mutually perpendicular directions to the direction, and a recording control unit which performs control so as to record a single pixel using a plurality of pulses upon recording of said image, the recording control unit performing control so that thermal patterns at neighboring pixels are shifted to perform the image recording.
It is preferable that the recording control unit makes a number of heating elements being activated, substantially uniform at each recording time.